字符串内部查找函数

字符串查找是程序中经常会碰到的,以下对常用字符串查找函数进行以下对比:

 

char* strchr( const char* str, int chr );
在str中查找第一次出现的chr，没找到则返回0

char* strrchr( const char* str, int chr );
在str中查找最后一次出现的chr，没找到则返回0

char* strstr( const char* str, const char* substr );
在str中查找第一次出现的substr，没找到则返回0

size_t strspn( const char* str, const char* chrset );
在str中查找 只包含在chrset中的字符 的最开始的最长字符数目
strspn( "cabbage", "abc" ) == 5;
strspn( "cabbage", "dc" ) == 1;
strspn( "cabbage", "d" ) == 0;
strspn( str, "abceg" ) == 7;

char* strspnp( const char* str, const char* chrset );
和strspn功能一样，只是返回指针
const char* str = "cabbage"
strspnp( str, "abc" ) == str+5;
strspnp( str, "dc" ) == str+1;
strspnp( str, "d" ) == str+0;
strspnp( str, "abceg" ) == 0; // 和strspn不一样

size_t strcspn( const char* str, const char* chrset );
在str中查找第一次出现在chrset中的字符位置，没找到则返回str结尾的'/0'的位置
strcspn( "xyzbxz", "abc" ) = 3
strcspn( "xyzbxz", "xyz" ) = 0
strcspn( "xyzbxz", "no match" ) = 6
strcspn( "xyzbxz", "" ) = 6
strcspn( "", "abc" ) = 0
strcspn( "", "" ) = 0

char* strpbrk( const char* str, const char* chrset );
和strcspn功能一样，只是返回指针
strpbrk( "xyzbxz", "abc" ) = "xyzbxz"+3
strpbrk( "xyzbxz", "xyz" ) = "xyzbxz"+0
strpbrk( "xyzbxz", "no match" ) = 0 // 和strcspn不一样
strpbrk( "xyzbxz", "" ) = 0 // 和strcspn不一样
strpbrk( "", "abc" ) = 0 // 和strcspn不一样
strpbrk( "", "" ) = 0 // 和strcspn不一样

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假如想将 "123@456@789" 分割成 "123" "456" "789" 当用 strchr
假如想将 "123@#456@#789" 分割成 "123" "456" "789" 当用 strstr
假如想将 "123@456#789@#0" 分割成 "123" "456" "789" "" "0" 当用 strcspn
假如想将 "123@456#789@#0" 分割成 "123" "456" "789" "0" 当用 strcspn/strspn

代码如下：（未曾测试过）
#include <stdio.h> #include <string.h> #include <assert.h> void split001( const char* str, const char chr ) { const char* p1 = str; for( const char* p2; (p2=strchr(p1,chr))!=0; p1=p2+1 ) { printf( "/"%.*s/"/n", p2-p1, p1 ); } printf( "/"%s/"/n", p1 ); } void split002( const char* str, const char* substr ) { assert( *substr ); const size_t substrlen = strlen(substr); const char* p1 = str; for( const char* p2; (p2=strstr(p1,substr))!=0; p1=p2+substrlen ) { printf( "/"%.*s/"/n", p2-p1, p1 ); } printf( "/"%s/"/n", p1 ); } void split003( const char* str, const char* substr ) { assert( *substr ); const char* p1 = str; for( const char* p2; p2=p1+strcspn(p1,substr), *p2; p1=p2+1 ) { printf( "/"%.*s/"/n", p2-p1, p1 ); } printf( "/"%s/"/n", p1 ); } void split004( const char* str, const char* substr ) { assert( *substr ); const char* p1 = str; for( const char* p2; p2=p1+strcspn(p1,substr), *p2; p1=p2+strspn(p2,substr) ) { printf( "/"%.*s/"/n", p2-p1, p1 ); } printf( "/"%s/"/n", p1 ); } int main( void ) { split001( "123@456@789", '@' ); printf( "---/n" ); split002( "123@#456@#789", "@#" ); printf( "---/n" ); split003( "123@456#789@#0", "@#" ); printf( "---/n" ); split004( "123@456#789@#0", "@#" ); printf( "---/n" ); return 0; }   

转自:周星星http://blog.vckbase.com/bruceteen/archive/2008/07/24/34495.html